White light consisting of wavelengths 380nm 750 nm isincident on a lead (Pb) sur

Question

White light consisting of wavelengths 380nm   750 nm isincident on a lead (Pb) surface. For which one of the followingranges of wavelengths will photoelectrons be emitted from the leadsurface that has a work function W0 = 6.63 x 10-19 J?
a. 380nm   750 nm b. 380 nm 630nm c. 380 nm 540nm d. 380 nm 410nm e. No photoelectrons will be emitted.
I know the answer is (e) butI don't know why.
a. 380nm   750 nm b. 380 nm 630nm c. 380 nm 540nm d. 380 nm 410nm e. No photoelectrons will be emitted.
I know the answer is (e) butI don't know why.

Explanation / Answer

work function W = hc / from this thershold wavelength = hc / W                                                 = [ ( 6.625 * 10 ^ -34 Js ) ( 3 * 10 ^ 8 m / s ) ] / [ 6.63 * 10 ^-19 J ]                                                  =2.9977 * 10 ^ -7 m                                                 = 299.77 nm If the wavelength of the light is greater than this wavelengththen photoelectric effect is occured. So, option ( e ) is correct

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